Device For Cooling An Exhaust Gas Stream Emerging From A Soot Particle Filter

ABSTRACT

Device for cooling an exhaust gas stream emerging from a soot particle filter, having an outlet connector provided on the soot particle filter for conveying out the exhaust gas stream, the outlet connector comprising a mouth region tapering in the direction of the exhaust gas stream, which region projects into an open end of an adjacent exhaust gas pipe in such a way that a reduced pressure relative to the surrounding environment may be produced in a suction region between the outlet connector and the exhaust gas pipe on passage of the exhaust gas stream.

FIELD OF THE DISCLOSURE

The disclosure relates to a device for cooling an exhaust gas streamemerging from a soot particle filter.

BACKGROUND OF THE DISCLOSURE

The exhaust gas standards enacted by the European Union provide for agradual reduction in the soot particles produced by diesel engines anddischarged into the environment with the engine exhaust gas. Sootparticle discharge is restricted by using soot particle filters, as arule with “wall-flow filters,” in which the engine exhaust gas passesthrough a porous filter wall of a ceramic or metallic material. In sodoing, the soot particles contained in the engine exhaust gas becomedeposited both on the surface and also inside the filter wall, such thatthe exhaust gas back-pressure increases as the degree of clogging of thefilter wall increases. To regenerate the soot particle filter, thedeposited soot particles are therefore burned at regular intervals, forwhich purpose the temperature of the engine exhaust gas is increasedfrom time to time to temperatures of over 500° C., for example using anoxidation catalytic converter connected upstream of the soot particlefilter. During regeneration, correspondingly high exhaust gastemperatures may occur at the tail pipe of the exhaust gas system(exhaust), which may lead to the formation of undesirable nitrogenoxides. Against this background, DE 10 2008 051 958 A1 discloses adevice for reducing the temperature of an exhaust gas stream emergingfrom a diesel particle filter, wherein cooler ambient air is admixedwith the waste gas stream by means of an air pump during regeneration ofthe diesel particle filter. Because the air pump is electricallycontrolled, the known device is of comparatively complex construction.

It is therefore the object of the present disclosure to simplify adevice of the above-mentioned type with regard to its structure.

This object is achieved by a device having the features of claim 1.

SUMMARY OF THE DISCLOSURE

A device for cooling an exhaust gas stream emerging from a soot particlefilter comprises an outlet connector provided on the soot particlefilter for conveying out the exhaust gas stream, the outlet connectorcomprising a mouth region tapering in the direction of the exhaust gasstream, which region projects into an open end of an adjacent exhaustgas pipe in such a way that a reduced pressure relative to thesurrounding environment may be produced in a suction region between theoutlet connector and the exhaust gas pipe on passage of the exhaust gasstream. More precisely, the reduced pressure is produced according tothe Venturi principle, wherein the mouth region of the outlet connectorextends in the manner of a nozzle into the open end of the exhaust gaspipe. The ambient air drawn into the exhaust gas pipe due to the reducedpressure leads in the process, depending on the temperature thereof, tocorresponding cooling of the exhaust gas stream.

Since the device is distinguished not only by a particularly simple, butsimultaneously also by an extremely compact structure, it is possible toaccommodate said device together with the soot particle filter inside anengine compartment of a motor vehicle operated by a diesel engine, inparticular, of an agricultural utility vehicle.

Cooling of the diesel engine is conventionally achieved by a hightemperature heat exchanger arranged in the engine compartment of themotor vehicle, which heat exchanger is a component of a liquid coolingcircuit connected with the diesel engine, the high temperature heatexchanger being exposed to cooling air by means of a fan unit, whichcooling air is drawn from the surrounding environment by way of aradiator grille and downstream filter inserts. Since the air conveyed inthis way into the engine compartment is largely free of contaminants,undesired clogging of the suction region formed between the outletconnector and the exhaust gas pipe is largely avoided. In addition, thecompression of the air located in the engine compartment, brought abouton the part of the fan unit, leads to an increased volumetric flow ratein the suction region and thus to more efficient cooling of the exhaustgas stream.

Preferably, the outlet connector is connected detachably to a fasteningflange of a filter housing surrounded by the soot particle filter.Accordingly, the fastening flange is a fixed component of the filterhousing and, as such, is welded or otherwise firmly connected thereto.The outlet connector may comprise a fastening portion, which may beplugged onto the fastening flange and which may be brought into airtightengagement with the fastening flange.

The detachable connection between the outlet connector and the fasteningflange of the filter housing may be produced in particular by means of aremovable spring clip. The spring clip here consists of a stainlesssteel or otherwise appropriately surface-treated steel alloy. Whenfitted, the spring clip grips around the outlet connector in the regionof the fastening portion in such a way that, by reducing thecircumference of the spring clip by means of a clamping screw or thelike, a clamp connection may be produced between the outlet connectorand the fastening flange of the filter housing. To improve the clampingaction, the outlet connector may comprise a plurality of fastening tabsextending transversely of the spring clip in the region of the fasteningportion.

Alternatively, the outlet connector may also be a fixed component of thefilter housing surrounded by the soot particle filter. The outletconnector is then welded or otherwise firmly connected to the filterhousing.

Preferably, the suction region takes the form of an annular gapextending radially between the outlet connector and the exhaust gaspipe. In this case both the outlet connector and the exhaust gas pipehave a substantially circular cross section at least in the suctionregion.

It has become clear that exhaust gas stream cooling efficiency may beoptimized if the ratio between an outer radius and an inner radius ofthe annular gap has a value in the range from 1.90 to 2.10. Thus, forexample, with an outer radius of 60 millimetres and an inner radius of29 millimetres, corresponding to a ratio of the two radii of approx2.07, the exhaust gas stream temperature may be reduced by more than200° C. It should be noted, however, that the above details are givenmerely by way of example and may differ to a greater or lesser degree asa function of the particular operating conditions.

The mouth region of the outlet connector preferably extends throughoutover its entire circumference at a distance from the open end of theexhaust gas pipe. In other words, the mouth region of the outletconnector is self-supporting relative to the open end of the exhaust gaspipe. The distance is selected such that, in the event of vibrationsoccurring between the outlet connector and the exhaust gas pipe as aresult of operation, the mouth region of the outlet connector may moveinside the open end of the exhaust gas pipe without touching it. Thisensures extensive mechanical decoupling of the two components.

It is additionally possible for the filter element to taper in thedirection of the outlet connector. The filter element tapers onlyinsofar as to rule out mutual contact between the outlet connector andthe exhaust gas pipe in the event of vibrations occurring between themas a result of operation.

Moreover, the suction region may be surrounded by a filter element, inparticular by a perforated mesh. The openings in the perforated mesh aredimensioned such that above all relatively coarse contaminants, whichwould lead rapidly to clogging or blocking of the suction region, arereliably retained. To increase corrosion resistance the perforated meshis made from an aluminium-coated steel alloy or the like.

The filter element may be arranged at the open end of the exhaust gaspipe and extend in the direction of the outlet connector. Moreprecisely, the filter element forms an extension arranged on the exhaustgas pipe, which beyond the suction region surrounds the outlet connectorover its entire circumference in the manner of a collar.

It is additionally possible for the filter element to taper in thedirection of the outlet connector. The filter element here tapers onlyinsofar as to rule out mutual contact between filter element and outletconnector in the event of vibrations occurring between the outletconnector and the exhaust gas pipe as a result of operation.

It is additionally feasible for the exhaust gas pipe to be surrounded bya touch guard. The touch guard takes the form in particular of a tubularcover, which is fitted along the outside of the exhaust gas pipe bymeans of a plurality of spacers. To prevent overheating of the exhaustgas pipe, the tubular cover may comprise a plurality of openings atleast in the region of an exhaust, which allow circulation of the airpresent between the exhaust gas pipe and the tubular cover.

The device will be described in greater detail below with reference tothe appended drawings, in which components of matching or comparablefunction are labelled with the same reference numerals. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective overall view of an exemplary embodiment of thedevice for cooling an exhaust gas stream emerging from a soot particlefilter on an agricultural utility vehicle, and

FIG. 2 is a detail view of the exemplary embodiment shown in FIG. 1 ofthe device in longitudinal section.

DETAILED DESCRIPTIONS OF THE DRAWINGS

The soot particle filter 16 accommodated together with the device 10 inan engine compartment 12 of the agricultural utility vehicle 14, in thepresent case, takes the form of a conventional wall-flow filter, theengine exhaust gas produced by a diesel engine 18 of the agriculturalutility vehicle 14 passing through a porous filter wall of a ceramic ormetallic material. In the process, the soot particles contained in theengine exhaust gas become deposited both on the surface and also insidethe filter wall of the soot particle filter 16. Since the exhaust gasback-pressure increases as the degree of clogging of the filter wallincreases, the deposited soot particles are burned at regular intervalsto regenerate the soot particle filter 16, for which purpose thetemperature of the engine exhaust gas is increased from time to time totemperatures of over 500° C. using an oxidation catalytic converterconnected upstream of the soot particle filter 16.

To cool the exhaust gas stream 20 emerging from the soot particle filter16, the device 10 comprises an outlet connector 22 provided on the sootparticle filter 16 for conveying out the filtered exhaust gas stream 20,the outlet connector 22 comprising a mouth region 24 tapering in thedirection of the exhaust gas stream 20, which region projects into anopen end 26 of an adjacent exhaust gas pipe 28 in such a way that areduced pressure relative to the surrounding environment 32 may beproduced in a suction region 30 between the outlet connection 22 and theexhaust gas pipe 28 on passage of the exhaust gas stream 20.

More precisely, the reduced pressure is produced according to theVenturi principle, wherein the mouth region 24 of the outlet connector22 extends in the manner of a nozzle into the open end 26 of the exhaustgas pipe 28. The ambient air 34 drawn into the exhaust gas pipe 28 dueto the reduced pressure leads in the process, depending on thetemperature thereof, to corresponding cooling of the exhaust gas stream20.

The outlet connector 22 is connected detachably to a fastening flange 36of a filter housing 38 surrounded by the soot particle filter 16. Thefastening flange 36 is a fixed component of the filter housing 38 and assuch is welded or otherwise firmly connected thereto. The outletconnector 22 comprises a fastening portion 40, which may be plugged ontothe fastening flange 36 and which may be brought into airtightengagement with the fastening flange 36.

The detachable connection between the outlet connector 22 and thefastening flange 36 of the filter housing 38 is produced by means of aremovable spring clip 42. The spring clip 42 here consists of astainless steel or appropriately surface-treated steel alloy. Whenfitted, the spring clip 42 grips around the outlet connector 22 in theregion of the fastening portion 40 in such a way that, by reducing thecircumference of the spring clip 42 by means of a clamping screw 44 orthe like, a clamp connection may be produced between the outletconnector 22 and the fastening flange 36 of the filter housing 38. Toimprove the clamping action, the outlet connector 22 comprises aplurality of fastening tabs 46 extending transversely of the spring clip42 in the region of the fastening portion 40.

According to an alternative configuration of the device according to thedevice 10, the outlet connector 22 is a fixed component of the filterhousing 38 surrounded by the soot particle filter 16.

The suction region 30 takes the form of an annular gap 48 extendingradially between the outlet connector 22 and the exhaust gas pipe 28,such that both the outlet connector 22 and the exhaust gas pipe 28 havea substantially circular cross section at least in the suction region30.

The ratio between an outer radius R_(a) and an inner radius R_(i) of theannular gap 48 has a value in the range from 1.90 to 2.10. Preferably,the outer radius R_(a) and the inner radius R_(i) amount, in each casetaking account of tolerances conventional in manufacturing, to 60millimetres and 29 millimetres respectively, corresponding to a ratioR_(a)/R_(i) of the two radii of approx 2.07.

The mouth region 24 of the outlet connector 22 preferably extendsthroughout over its entire circumference at a distance from the open end26 of the exhaust gas pipe 28. The distance is selected such that, inthe event of vibrations occurring between the outlet connector 22 andthe exhaust gas pipe 28 as a result of operation, the mouth region 24 ofthe outlet connector 22 may move inside the open end 26 of the exhaustgas pipe 28 without touching it. In this way, extensive mechanicaldecoupling of the two components 22, 28 is achieved.

Furthermore, the suction region 30 is surrounded by an optional filterelement 50 in the form of a perforated mesh 52. The openings 54 in theperforated mesh 52 are dimensioned such that above all relatively coarsecontaminants, which would lead rapidly to clogging or blocking of thesuction region 30, are reliably retained. To this end the diameter ofthe openings 54 is selected to be smaller than the gap size R_(a)-R_(i)of the suction region 30. To increase corrosion resistance theperforated mesh 52 is made from an aluminium-coated steel alloy or thelike.

The filter element 50 is arranged at the open end 26 of the exhaust gaspipe 28 and extends in the direction of the outlet connector 22. Moreprecisely, the filter element 50 forms an extension arranged on theexhaust gas pipe 28, which beyond the suction region 30 surrounds theoutlet connector 22 over its entire circumference in the manner of acollar.

In addition, the filter element 50 is tapered in the direction of theoutlet connector 22. The filter element 50 tapers only insofar as torule out mutual contact between the filter element 50 and the outletconnector 22 in the event of vibrations occurring between the outletconnector 22 and the exhaust gas pipe 28 as a result of operation.

According to FIG. 1, the exhaust gas pipe 28 is surrounded at least inplaces by a touch guard 56. The touch guard 56 takes the form of atubular cover 58, which is fitted along the outside of the exhaust gaspipe 28 by means of a plurality of spacers. To prevent overheating ofthe exhaust gas pipe 28, the tubular cover 58 comprises a plurality ofopenings 62 at least in the region of an exhaust 60, which allowcirculation of the air present between the exhaust gas pipe 28 and thetubular cover 58.

Although the agricultural utility vehicle 14 shown in FIG. 1 is, by wayof example, a tractor, it is likewise feasible for the device 10 to beused with any other desired diesel-engined motor vehicles. In addition,it may also be used in stationary applications, such as for example adiesel-engined power generator or the like.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description isto be considered as exemplary and not restrictive in character, it beingunderstood that illustrative embodiments have been shown and describedand that all changes and modifications that come within the spirit ofthe disclosure are desired to be protected. It will be noted thatalternative embodiments of the present disclosure may not include all ofthe features described yet still benefit from at least some of theadvantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations that incorporate one or more ofthe features of the present disclosure and fall within the spirit andscope of the present invention as defined by the appended claims.

1. A device for cooling an exhaust gas stream emerging from a sootparticle filter, wherein an outlet connector is provided on the sootparticle filter for conveying out the exhaust gas stream, the outletconnector comprising a mouth region tapering in the direction of theexhaust gas stream, the region projects into an open end of an adjacentexhaust gas pipe in such a way that a reduced pressure relative to thesurrounding environment may be produced in a suction region between theoutlet connector and the exhaust gas pipe on passage of the exhaust gasstream.
 2. The device according to claim 1, wherein the outlet connectoris connected detachably with a fastening flange of a filter housingsurrounded by the soot particle filter.
 3. The device according to claim1, wherein the detachable connection between the outlet connector andthe fastening flange of the filter housing may be produced by means of aremovable spring clip.
 4. The device according claim 1, wherein theoutlet connector is a fixed component of the filter housing surroundedby the soot particle filter.
 5. The device according to claim 1, whereinthe suction region takes the form of an annular gap extending radiallybetween the outlet connector and the exhaust gas pipe.
 6. The deviceaccording to claim 5, wherein the ratio between an outer radius and aninner radius of the annular gap has a value in the range from 1.90 to2.10.
 7. The device according to claim 1, wherein the mouth region ofthe outlet connector extends throughout over its entire circumference ata distance from the open end of the exhaust gas pipe.
 8. The deviceaccording to claim 1, wherein the suction region is surrounded by afilter element, in particular by a perforated mesh.
 9. The deviceaccording to claim 8, wherein the filter element is arranged at the openend of the exhaust gas pipe and extends in the direction of the outletconnector.
 10. The device according to claim 8, wherein the filterelement is tapered in the direction of the outlet connector.
 11. Thedevice according to claim 8, wherein the filter element tapers in thedirection of the outlet connector.
 12. The device according to claim 1,wherein the exhaust gas pipe is surrounded at least in places by a touchguard.
 13. A motor vehicle having a device for cooling an exhaust gasstream emerging from a soot particle filter, wherein an outlet connectoris provided on the soot particle filter for conveying out the exhaustgas stream, the outlet connector comprising a mouth region tapering inthe direction of the exhaust gas stream, the region projects into anopen end of an adjacent exhaust gas pipe in such a way that a reducedpressure relative to the surrounding environment may be produced in asuction region between the outlet connector and the exhaust gas pipe onpassage of the exhaust gas stream.
 14. The motor vehicle of claim 13,wherein the device is positioned in an engine compartment.
 15. The motorvehicle of claim 13, wherein the motor vehicle is an agriculturalutility vehicle.